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<groolot>
sébastien es-tu là ?
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<sb0_>
groolot: yes
<groolot>
sb0_: te rappelles-tu de notre rencontre à Nice l'année passée ?
<sb0_>
probably
<sb0_>
I don't remember your irc nickname, though
<sb0_>
aah, David from groolot
<sb0_>
Gregory
<sb0_>
sorry
<sb0_>
what's up?
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<sb0>
wpwrak, I think I remember you used some open source analog circuit simulator a few times. which is it, and is it good?
<sb0>
is it geda+ngspice?
* aeris
blouargh
<aeris>
Sorry, spice effect...
<sb0>
rjo, 20pF is quite a load at 50MHz/50V. I guess there's no easy way to reduce that?
<davidc__>
sb0: probe capacitance?
<davidc__>
sb0: what are you trying to reduce?
<sb0>
davidc__, ion trap electrode capacitance
<davidc__>
sb0: oh, heh. yeah, thats not something I can really help ya optimize :)
<davidc__>
get a more powerful amp? :)
<sb0>
that's a possibility, but in class A (it also needs to be wideband) that would dissipate dozens of watts
<sb0>
per electrode ...
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<davidc__>
sb0: couldn't you make it a resonant circuit? how wideband does it need to be?
<sb0>
yeah, maybe there are some power factor correction options
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<wpwrak>
someone who doesn't stay on 24/7, how quaint. that simulator would be qucs. rather nice to use, just needs a bit of trial & error to actually get it to accept some simulations.
<rjo>
sb0: 10pF might be more typical. but yes. there is also some inductance so the impedance is reduced a bit.
<rjo>
yep qucs is good.
<rjo>
and 20pF is not a real load, it is purely imaginary ;P
<larsc>
its all in your head
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<davidc__>
rjo: how wide bandwidth does the probe need to be?
<davidc__>
rjo: IE, can you just make it resonant so its nice and high impedance?
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<rjo>
davidc__: not a probe. an ion trap electrode.
<rjo>
davidc__: usually i would just go for a Q~500 helical resonator but in this case changes to the load capacitance and slight coupling between the electrodes must not change the phase at the electrode. thus very wideband ;)
<rjo>
larsc: if my head is in quadrature, yes.
<davidc__>
sorry, electrode
<davidc__>
rjo: pfft, just fix that with DSP ;)
<davidc__>
(I kid)
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<rjo>
davidc__: we do that. but the way to measure it is a bit complicated: using the ion itself.
<davidc__>
rjo: does the coupling change at runtime or just buildtime?